Year	Percent
1991-01-01	6.4
1992-01-01	7.0
1993-01-01	7.2
1994-01-01	7.0
1995-01-01	6.7
1996-01-01	6.8
1997-01-01	6.5
1998-01-01	6.4
1999-01-01	6.1
2000-01-01	5.7
2001-01-01	5.9
2002-01-01	6.5
2003-01-01	6.6
2004-01-01	6.4
2005-01-01	6.2
2006-01-01	5.8
2007-01-01	5.4
2008-01-01	5.8
2009-01-01	8.0
2010-01-01	8.1
2011-01-01	7.6
2012-01-01	7.4
2013-01-01	7.1
2014-01-01	6.4
2015-01-01	5.8
2016-01-01	5.5